Much progress has been made in the art of transmitting digital video signals for use by receiving terminals in a variety of applications such as video phones, video conference, and the like. High speed transmission services, such as T 1.5 carrier, ISN, 168 kilobit, 45 Megabit, ISDN&lt; and others are available to accommodate the high bandwidth required for video information transmission. In addition, data compression-decompression techniques are used to pack more video data into a given bandwidth which aids real time video and other applications.
Notwithstanding these and other advances, the high data content of full motion video prior art systems still require an undesirable technical trade-off between tile nature of the transmission capacity and the informational content required per unit of time for satisfactory video images. Serious bandwidth constraints arise when transmission occurs over analog telephone lines or when color information is part of the video informational content.
Data compression techniques only partially relieve these problems by reducing somewhat the number of bits needed to convey video images. In some cases, these techniques introduce other quality problems such as jerky motion caused by low frame rate transmission or display.
Today it is common practice to use various techniques in standard television and video to reduce noise, enhance picture sharpness, reduce cross-color effects, and otherwise process the video signals for enhancement before used for display. Certain well known techniques serving to reduce noise include processing video signals through a buffer that averages (pixel-by-pixel) two or more successive line, field or frame values so that noise , but not information, averages out. See the following U.S. patents:
Purports to show a noise reduction system using a frame buffer and frame averaging means: U.S Pat. No. 4,679,086.
Purports to show recursive noise reduction system with frame buffer with additional structure:
______________________________________ U.S. Pat. No.: 4,860,104 U.S. Pat. No.: 4,809,069 4,639,783 4,485,403 4,388,729 4,296,436 4,240,106 4,064,530 ______________________________________
One major problem resulting from the use of this prior art technique relates to visual "smearing" of the displayed images that move over time. See U.S. Pat. No. 4,388 729. Motion detection and adaptive circuits have been developed to reduce the averaging effects (and thereby the smearing) for those parts of the displayed field/frame where motion is detected. These circuits generate motion compensation signals to reduce or control the smearing effects. See U.S. Pat. Nos. 4,296,436 and 4,860,104.